Roxio has just released Xingtone Ringtone Maker.
The only real GREAT thing about this is that it will create native ringtones in the amr format. All the other formats that it generates/converts can be accomplished using other applications, which may actually be free.

I should probably point out that the amr format is the native Treo 650 ringtone format. This means that you no longer need 3rd-party crash prone apps to use the sound of your dog barking as a ringer. You can now just record your dog and then convert the sound to amr. Then transfer that as a ringtone to your Treo.